The present invention relates to a composite material comprising a substrate and a coating based on a powder polymeric composition covering the said substrate and to a process for the preparation of this composite material such that the energy necessary for forming a film of the powder polymeric composition on the substrate is transmitted by an electromagnetic radiation in the microwave region.
Various techniques for ensuring the drying and/or the film formation of polymeric compositions by electromagnetic radiation in the microwave region are known.
French Patent published under No. 2,176,395 in the name of Donald Macpherson Group Limited describes the drying, by the action of microwaves, of a latex or of a dispersion of at least 2 polymers whose film-forming temperatures are close to room temperature.
French Patent published under No. 2,458,323 describes a process for coating a substrate of the glass type with a liquid coating based on heat-curable polymers which are dried and cured by an application of microwave energy.